Methanol-to-olefin processes are well described in the art. Typically, methanol-to-olefin processes are used to produce predominantly ethylene and propylene. An example of such a methanol-to-olefin process is described in WO-A 2006/020083. In the process of WO-A 2006/020083, the methanol is first converted into dimethylether (DME) prior to be subjected to a conversion to olefins, thereby reducing the amount of water produced during the conversion to olefins. Both methanol and DME are suitable feedstocks for a Methanol-to-olefin process and therefore such processes are also generally referred to as oxygenate-to-olefin (OTO) processes.
Ethanol can also be converted in to ethylene. U.S. Pat. No. 4,207,424 describes a process wherein ethanol is converted to ethylene in a dehydration reaction using an alumina catalyst. U.S. Pat. No. 4,727,214 describes a process wherein ethanol is converted to ethylene using a crystalline zeolitic catalyst. Other ethanol dehydration processes have been described extensively in the prior art. A disadvantage of these processes is that only ethylene is formed in an ethanol dehydration process, where methanol-to-olefin processes convert methanol or DME to a product slate containing both ethylene and propylene. Ethanol is mentioned, among numerous other oxygenates, in several prior art documents, including for instance US20090105429, US20090187058, US20100298619, US20090187059, US20090187057, US20090187056 as an optional feedstock to an oxygenate to olefins process. However none of these documents describe the conversion of ethanol in any detail, nor do they provide any information on the expected product slate.
In EP2108637, a two step process is proposed to convert ethanol into ethylene and propylene. In the process of EP2108637, ethanol is dehydrated in a first process step. The ethanol is dehydrated to ethylene by contacting the ethanol with a silicalite (SAR 270) catalyst. In a subsequent process step the obtained ethylene is provided together with a C4+ fraction, for instance obtained from an FCC, to an olefin cracking process (OCP), wherein part of the ethylene is converted with the C4+ olefins to propylene.
In the example described in EP2108637, approximately 25 wt % of the ethylene obtained from dehydrating ethanol is converted to propylene and the effluent of the OCP reactor containing ethylene and propylene at a weight ratio of approximately 2 to 1. In contrast most methanol-to-olefin processes convert the methanol or DME to an olefinic product that contains significantly more propylene.
There is a need in the art to produce olefinic products from ethanol-comprising feedstocks with an increased propylene yield, while maintaining a high ethylene yield.